NWCG Glossary of Wildland Fire (PMS 205)

Term	Steward	Status	Definition
Water Expansion System (WES)	ETSC Equipment/Technology Subcommittee	Approved	Apparatus utilizing a pressurized tank, hose, and nozzle for producing foam by injection of compressed air or gas into a liquid stream downstream from the pumping source. The liquid stream must contain a suitable foaming agent.
water extraction	MFES Mobile Fire Equipment Subcommittee	Approved	The pH content of a hose jacket determined after boiling in distilled water in a laboratory test.
water hammer	ETSC Equipment/Technology Subcommittee	Approved	A force created by the rapid acceleration or deceleration of water, commonly created by opening or closing a valve too quickly. Pressures developed in a water hammer, proportional to the mass multiplied by the square of the velocity, can damage a pipe or hose.&nbsp;
water source	IOSC Incident Operations Subcommittee	Approved	Any strategically located supply of water that is readily available for pumps, tanks, trucks, helicopters, or fire camp use.
water source type	IOSC Incident Operations Subcommittee	Approved	The type of water source.
water supply map	GISC Geospatial Information Subcommittee	Approved	A map showing location of supplies of water readily available for pumps, tanks, trucks, camp use, etc.
water tender	ETSC Equipment/Technology Subcommittee	Approved	Any ground vehicle capable of transporting specified quantities of water.
water thief	ETSC Equipment/Technology Subcommittee	Approved	A type of bleeder valve designed for installation at convenient points in hose lines to permit drawing off water for filling backpack pumps or other use without interfering with pump or nozzle operation.
waterway	IFPC Interagency Fire Planning Committee	Requested	Any body of water including lakes, rivers, streams and ponds whether or not they contain aquatic life.
wave	IWSC Incident Weather Subcommittee	Approved	A disturbance that transfers energy from one point to another point and may take the form of a deformation of pressure or temperature. In the atmosphere such disturbances may result in major storms or merely result in changes in cloud, wind and temperature conditions. Development of a wave on a front usually slows the advance of the front due to transfer of energy to the wave development and movement.&nbsp;
weather advisory	IWSC Incident Weather Subcommittee	Approved	In aviation forecasting, an expression of hazardous weather conditions not predicted in the zone weather forecast, as they affect the operation of air traffic.
weather concerns	PMC Fire Planning Management Committee, FESC Fire Environment Subcommittee	Approved	A field collected in the ICS 209 containing a brief summary of how the current weather is affecting the incident and how the anticipated weather will affect the incident.
weighted monthly occurrence	FDSC Fire Danger Subcommittee	Approved	Part of the National Fire Danger Rating System (NFDRS).&nbsp; Number used to determine seasonal risk class for a protection unit, calculated by multiplying peak monthly average by two and adding seasonal monthly average.
well-defined (data quality)	IMC Integration Management Committee, DISC Data Integration Subcommittee	Approved	Master and metadata standards exist and data complies with the standard.
wet	FBC Finance/Business Management Committee	Approved	The contractor furnishes all equipment operating supplies.
wet foam	ETSC Equipment/Technology Subcommittee	Approved	A low expansion foam type with few and varied bubbles and rapid drain time which is used for rapid penetration and fire extinguishment.
wet line	IOSC Incident Operations Subcommittee	Approved	A line of water, or water and chemical retardant, sprayed along the ground, and which serves as a temporary control line from which to ignite or stop a low-intensity fire.
wet storage	ETSC Equipment/Technology Subcommittee	Approved	Fire retardants mixed with water and stored in tanks at air attack bases for immediate use by airtankers.
wet water	ETSC Equipment/Technology Subcommittee	Approved	Water with added chemicals, called wetting agents, that increase water's spreading and penetrating properties due to a reduction in surface tension.
wet-bulb depression	IWSC Incident Weather Subcommittee	Approved	The difference between the wet and dry-bulb temperatures recorded by a psychrometer; used in conjunction with the dry-bulb temperature as a measure of the relative humidity of the air.
wet-bulb temperature	IWSC Incident Weather Subcommittee	Approved	The lowest temperature to which air can be cooled by evaporating water into it at a constant pressure when the heat required for evaporation is supplied by the cooling of the air. It is measured by the wet bulb thermometer, which usually employs wetted wicking on the bulb as a cooling (through evaporation) device.
wet-bulb thermometer	IWSC Incident Weather Subcommittee	Approved	In a psychrometer, the thermometer with its bulb covered with a jacket of clean muslin which is saturated with distilled water before an observation.
wetting agent	ETSC Equipment/Technology Subcommittee	Approved	A chemical that when added to water reduces the surface tension of the solution and causes it to spread and penetrate exposed objects more effectively than the untreated water.
wetting rain	IWSC Incident Weather Subcommittee	Approved	A widespread rain that over an extended period of time significantly reduces fire danger. One-tenth of an inch may be sufficient to reduce fire danger in grass fuel models. One half inch may be necessary for timber fuels under closed canopies.
wheelbase	ETSC Equipment/Technology Subcommittee	Approved	The distance from the centerline of the front axle to the centerline of the rear axle. For a tandem rear axle vehicle the center line is midpoint between the centers of the two rear axles.

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